From 55368223cde4f19b4cd97eff7ea82b4a85a7a04c Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 10 Dec 2008 17:11:18 +0000
Subject: [PATCH] Tweak the tree descent loop in fsm_search_avail to not look
at the right child if it doesn't need to. This saves some miniscule number
of cycles, but the ulterior motive is to avoid an optimization bug known to
exist in SCO's C compiler (and perhaps others?)
---
src/backend/storage/freespace/fsmpage.c | 27 ++++++++++++++-----------
1 file changed, 15 insertions(+), 12 deletions(-)
diff --git a/src/backend/storage/freespace/fsmpage.c b/src/backend/storage/freespace/fsmpage.c
index 3a25c959299..a4479e88c07 100644
--- a/src/backend/storage/freespace/fsmpage.c
+++ b/src/backend/storage/freespace/fsmpage.c
@@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/freespace/fsmpage.c,v 1.2 2008/10/07 21:10:11 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/freespace/fsmpage.c,v 1.3 2008/12/10 17:11:18 tgl Exp $
*
* NOTES:
*
@@ -243,17 +243,20 @@ fsm_search_avail(Buffer buf, uint8 minvalue, bool advancenext,
*/
while (nodeno < NonLeafNodesPerPage)
{
- int leftnodeno = leftchild(nodeno);
- int rightnodeno = leftnodeno + 1;
- bool leftok = (leftnodeno < NodesPerPage) &&
- (fsmpage->fp_nodes[leftnodeno] >= minvalue);
- bool rightok = (rightnodeno < NodesPerPage) &&
- (fsmpage->fp_nodes[rightnodeno] >= minvalue);
-
- if (leftok)
- nodeno = leftnodeno;
- else if (rightok)
- nodeno = rightnodeno;
+ int childnodeno = leftchild(nodeno);
+
+ if (childnodeno < NodesPerPage &&
+ fsmpage->fp_nodes[childnodeno] >= minvalue)
+ {
+ nodeno = childnodeno;
+ continue;
+ }
+ childnodeno++; /* point to right child */
+ if (childnodeno < NodesPerPage &&
+ fsmpage->fp_nodes[childnodeno] >= minvalue)
+ {
+ nodeno = childnodeno;
+ }
else
{
/*
--
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